1. Field of the Invention
The present invention generally relates to a piezoelectric actuator having a piezoelectric element that warps in response to applied electric power to minutely move an objective part relative to a base part. In particular, the present invention relates to a wiring connecting structure capable of achieving wiring to the piezoelectric element without damaging the piezoelectric element or deteriorating the reliability thereof. The present invention also relates to the piezoelectric actuator and a head suspension employing the piezoelectric actuator.
2. Description of Related Art
Small-sized, precision information devices are rapidly advancing, and for use with such devices, needs for micro-actuators capable of conducting positioning control for very small distances are increasing. Such micro-actuators are highly needed by, for example, optical systems for correcting focuses and inclination angles, ink jet printers for controlling ink heads, and magnetic disk drives for controlling magnetic heads.
The applicant of the present invention has proposed in Japanese Unexamined Patent Application Publication No. 2002-50140 a head suspension for a disk drive, having a base plate, a connection plate attached to the base plate and provided with a hinge thinner than the base plate, a load beam attached to the connection plate, a flexure attached to the load beam and provided with a slider, and a pair of piezoelectric elements.
This related art employs a dual actuator system that involves, for a precise positioning purpose, a voice coil motor and the piezoelectric elements made of, for example, PZT (lead zirconate titanate). The piezoelectric elements form a piezoelectric actuator to minutely drive a front end of the load beam or only the slider in a widthwise direction (sway direction) of the head suspension. Compared with a single actuator system employing only the voice coil motor, the dual actuator system employing the voice coil motor and piezoelectric actuator more precisely positions a magnetic head attached to a front end of the head suspension.
An important issue for the head suspension employing the dual actuator system is how to supply electricity to the piezoelectric elements.
A technique to approach this issue is disclosed in Japanese Unexamined Patent Application Publication No. 2003-61371 (in particular, FIGS. 9 and 10 thereof). This related art arranges a pair of wires on the head suspension. One of the wires is connected through wire bonding to a base electrode and the other wire is connected through wire bonding to an exposed part of the top face of each piezoelectric element.
This related art has a risk of cracking the piezoelectric element because, to secure a bonding strength, it applies a local stress on the brittle piezoelectric element when bonding the wire to the piezoelectric element.
If the wire bonding process is carried out with a reduced force not to crack the piezoelectric element, the bonding strength will be insufficient to deteriorate the reliability of electric connection to the piezoelectric element.
In this way, it is very difficult to carry out wiring to the piezoelectric element without damaging the same.